EFFECT OF BLOOD PLASMA LIPOPROTEINS ON HYDROXYLATION OF BENZO[a]PYRENE IN LIVER MICROSOMES OF RATS
L.M. Polyakov, R.A. Knyazev, N.V. Trifonova, M.V. Kotova, E.I. Solovyova, A.V. Ryabchenko
Research Institute of Biochemistry of Federal Research Center of Fundamental and Translational Medicine, 630117, Novosibirsk, Timakov str., 2
Keywords: benzo[a]pyrene, rat liver microsomes, blood plasma lipoproteins
Abstract
This work presents the characteristics of the catalytic activity of hydroxylation of benzo[a]pyrene (B[a]P) in rat liver microsomes using plasma lipoproteins (LP) (VLDL, LDL, HDL) as transport forms of B[a]P. The aim of the study was: to study the effect of the LP-component of the LP-B[a]P complexes on the rate of B[a]P hydroxylation in rat liver microsomes. The studies were carried out on the microsomal fraction of rat liver using B[a]P as a substrate, ultracentrifugation of individual fractions of VLDL, LDL, HDL plasma, and spectrofluorimetric determination of the activity of arylhydrocarbonhydroxylase. In work on microsomes of rat liver the rate of hydroxylation of B[a]P in free form and in the form of B[a]P complexes with various fractions of LP was analyzed. The analysis showed that the arylhydrocarbonhydroxylase activity (pmol 3-OH-B[a]P in 1 min per 1 mg of protein) decreases in the complex form B[a]P with LP. So for transport form B[a]P with HDL the decrease was by 22%, for transport form B[a]P with VLDL the decrease was 30%, and for transport form B[a]P with LDL it was 52%. It should be noted that K m for the substrate remained practically unchanged in all forms. The V max and K m values indicate that the LP component in complexes with B[a]P can be a noncompetitive inhibitor of B[a]P hydroxylation in rat liver microsomes.
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